2. Model and Methods
Two types of AC-field coils are developed to generate
50-Hz AC magnetic fields in the bore of a
super-conducting coil. Those coils generate an AC-field
parallel (Helmholtz-type, Fig.2) or perpendicular (Saddle
-type. Fig.?) to the static field. The design parameter of
the, saddle type coil is obtained by optimizing the
uniformity of the coil in exposure region [ 11 (Fig. 4).